Environmental Engineering Reference
In-Depth Information
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Fig. 12.4
Changes in Australian hematite ore price for Japan
12.2
Lifetimes of Metal Resources
Figure
12.5
shows the relationship between annual consumption of various elements
and their proportion in the earth crust; that is a modified Clark Number
1
. In the figure,
elements are sorted into three groups; chalcophile, siderophile and lithophile, accord-
ing to the classification by Goldschmidt (
1937
). In this graph, the chalcophile ele-
ments which are aligned along the orange line (that is metal resources which are pres-
ent at lower concentrations but are being consumed in larger amounts) are exhaust-
ible. It is no surprise that gold and silver are included in such elements but it is also
notable that common metals like copper and lead are located there. Iron is one of the
siderophile elements; its consumption is extremely large but the quantity of resources
existing is also large. Therefore, it is one of the elements where it is not necessary
to be concerned about the resource's exhaustibility. It is also worthy of mention that
another element, indium is classified as one of lithophile elements, whose resources
are usually sufficient. However, indium has been mainly produced as a byproduct of
the zinc refining process and supply is therefore determined by the demand for zinc.
As the demand for indium for use as ITO (tin-doped indium oxide) materials has
increased rapidly (for electrodes in liquid crystal panels and organic electrolumines-
cence), demand has exceeded supply and indium broke the supply-demand balance
in the short-term. Such imbalances can only be reversed by development of new
resources, which may be stimulated by the resulting increase in the price of indium.
From the point of view of different availabilities and rates of consumption,
some observations can be made on the ways in which the static lifetimes of several
1
Clarke's numbers express the average content of the chemical elements in the earth's crust and
other geochemical and cosmo-chemical systems.
